Yang Qizong, Chen Chia-Chien, Ramos Raddy L, Katz Elizabeth, Keller Asaf, Brumberg Joshua C
Department of Psychology, Queens College , CUNY, Flushing, NY , USA .
Somatosens Mot Res. 2014 Jun;31(2):78-93. doi: 10.3109/08990220.2013.869495. Epub 2014 Jan 7.
Corticothalamic (CT) feedback plays an important role in regulating the sensory information that the cortex receives. Within the somatosensory cortex layer VI originates the feedback to the ventral posterior medial (VPM) nucleus of the thalamus, which in turn receives sensory information from the contralateral whiskers. We examined the physiology and morphology of CT neurons in rat somatosensory cortex, focusing on the physiological characteristics of the monosynaptic inputs that they receive from the thalamus. To identify CT neurons, rhodamine microspheres were injected into VPM and allowed to retrogradely transport to the soma of CT neurons. Thalamocortical slices were prepared at least 3 days post injection. Whole-cell recordings from labeled CT cells in layer VI demonstrated that they are regular spiking neurons and exhibit little spike frequency adaption. Two anatomical classes were identified based on their apical dendrites that either terminated by layer V (compact cells) or layer IV (elaborate cells). Thalamic inputs onto identified CT-VPM neurons demonstrated paired pulse depression over a wide frequency range (2-20 Hz). Stimulus trains also resulted in significant synaptic depression above 10 Hz. Our results suggest that thalamic inputs differentially impact CT-VPM neurons in layer VI. This characteristic may allow them to differentiate a wide range of stimulation frequencies which in turn further tune the feedback signals to the thalamus.
皮质丘脑(CT)反馈在调节皮层接收的感觉信息方面发挥着重要作用。在体感皮层中,第VI层发出对丘脑腹后内侧(VPM)核的反馈,而VPM核反过来又从对侧触须接收感觉信息。我们研究了大鼠体感皮层中CT神经元的生理学和形态学,重点关注它们从丘脑接收的单突触输入的生理特征。为了识别CT神经元,将罗丹明微球注入VPM,并使其逆向运输到CT神经元的胞体。在注射后至少3天制备丘脑皮质切片。对第VI层标记的CT细胞进行全细胞记录表明,它们是规则发放的神经元,且几乎没有放电频率适应性。根据其顶端树突的终止位置,可将其分为两类解剖学类型,一类在第V层终止(紧密细胞),另一类在第IV层终止(精细细胞)。对已识别的CT-VPM神经元的丘脑输入在很宽的频率范围(2-20Hz)内表现出双脉冲抑制。刺激串在10Hz以上也会导致显著的突触抑制。我们的结果表明,丘脑输入对第VI层的CT-VPM神经元有不同的影响。这一特性可能使它们能够区分广泛的刺激频率,进而进一步调整对丘脑的反馈信号。